The present invention relates to a heat and humidification system for use with a high frequency jet ventilator humidification system in delivering respirable gas to the lungs of a patient. While the use of high frequency jet ventilator in a variety of clinical situations is gaining increased acceptance in the medical profession, there are still important technical problems to be solved in the heating and humidification of the delivered gas. It has been found that conventional humidifiers are unsuitable in this application for at least two reasons: first, they are not designed to withstand the relatively high system pressures; and second, the compressible gas volumes of even the smallest infant humidifiers attenuate or damp the jet pulsations, thereby hampering their transmission to the patient's airways.
To avoid the problems of the convention humidifier, humidification of the delivered gas is sometimes accomplished by injecting water in droplet form into the gas from the jet ventilator with an infusion pump. In this technique, the water from the infusion pump can be heated but there is no provision for heating the jet gas. In such systems the jet ventilator is used with a separate circuit that provides heated and humidified gas at the point of connection to the patient's endotracheal tube. This allows the patient to breath conditioned gas during spontaneous respirations and permits independent control of continuous positive airway pressure. Some of the gas in the continuous positive airway pressure circuit may be entrained during the jet pulsations, thereby increasing the humidity and temperature of the gas delivered to the patient. In general, however, the gas reaching the patient's airways is cooler than body temperature, and most of the water it carries is delivered in particulate form. While these conditions may be acceptable for the high frequency jet ventilation of adults, they can cause problems of fluid overload, electrolyte imbalance, and hypothermia in premature infants and children. In addition, cold nebulized water and low inspired air temperatures may contribute to pulmonary damage during intermittent positive-pressure ventilation. Therefore, there is a need for an improved system which would condition the gas delivered by the jet ventilator so that the gas is free of particulate water but saturated with water vapor at body temperature.
In addition, it has been found that conventional humidifiers require a great deal of maintenance and repair. Often, the heat exchanger and delivery circuit are not reusable since they cannot be easily cleaned and sterilized. Thus, there is a need for an improved system which does not require a great deal of maintenance and repair. There is a further need for a system which is reusable and which can be easily cleaned and sterilized.